We are proposing to determine the effect of steroid hormones on receptors for gonadotropin-releasing hormone (Gn-RH) in the ovine adenohypophysis. Specific binding of Gn-RH membranes of adenohypophyseal tissue from long term castrated ewes will be compared to specific binding of Gn-RH to adenohypophyseal tissue from castrated ewes treated with estrogens, progestins or combinations of these steroids. In conjunction with Scatchard plot analysis of the data these studies will allow us to determine if steroids alter the number of Gn-RH. We further propose to compare the binding of analogs of Gn-RH to membranes of ovine adenohypophyseal tissue with their ability to release LH and FSH in vivo and from dispersed ovine adenohypophyseal cells. The combination of these techniques will allow us to determine the potential of analogs of Gn-RH for use as contraceptives or fecundity agents.